A prior carrier tool having an exchangeable tool head is described in EP 1 476 269 B1. The modular carrier tool described therein comprises a carrier in which a tool head is inserted on the front-end in a reversible exchangeable manner. The tool head is accepted exclusively in a clamping manner by a head retainer. For this purpose, the head retainer comprises two clamping webs that are formed separately from each other on the front-end of the carrier and extend in an axial direction, which clamp the tool head in between themselves. During assembly, the tool head is first inserted in an axial direction and then rotated against the cutting direction, whereby the clamping surfaces are brought into contact with each other. In addition to clamping in a radial direction, a pull-out protection acting in an axial direction is also accomplished. During assembly, the tool head is pressed against the clamping webs in an axial direction. For this purpose, the tool head has plane underhead bearing surfaces running perpendicularly to a central longitudinal axis, with which the tool head supports itself on corresponding bearing surfaces on the clamping webs.
For this particular type of modular carrier tool, no further fastening elements, such as, for example, fastening screws are provided. The tool head is exchanged and replaced by a new one as soon as it is worn out. Therefore, a multitude of tool heads are inserted into the carrier throughout its lifetime. It is possible that throughout the course of the service life the elasticity of the freely protruding clamping webs decreases and with that the clamping force exerted unto the tool head weakens, so that as the service life of the carrier progresses, the tool head is no longer held in an adequately fail-safe manner.